In fact, this year, Chipotle, which is growing so quickly that it's opening about three new locations each week, will slowly braise and sell about 120 million pounds of naturally raised pork, chicken and beef that meets its antibiotic-free standards.

The company's transition to antibiotic-free meat began more than a decade ago when Chipotle realized its pork wasn't selling very well. And Steve Ells, the founder, wanted to make some changes.

He stumbled upon an article called "The Lost Taste of Pork" in The Art of Eating, a boutiquey, food-lover's journal, which detailed the practices of Paul Willis, a family farmer in Iowa. Willis raises pigs on pasture, the old-fashioned way. At the time, Willis' methods were a radical departure from the large, industrial operations that confine pigs indoors and feed them regular doses of antibiotics.

In the article, published back in 1999, writer Edward Behr described a thick pork chop he'd eaten at Chez Panisse in Berkeley that came from a pig raised on the Iowa farm. "It was the best pork I'd ever eaten — tender and somewhat fatty," he wrote. Ells was intrigued.

Ells ordered some pork from Willis, who had teamed up with Niman Ranch in Iowa, and Chipotle's customers responded: Despite a jump in price from $4.50 to $5.50 for a carnitas burrito, sales improved.

"We started selling twice as many carnitas as we had been before," Chipotle's Chris Arnold told me. He acknowledged that it's hard to know whether people truly detected a big difference, or if the in-store marketing about the switch to all-natural, antibiotic-free pigs caught people's attention. Either way, it set Chipotle on a new course.

I reached out to Willis, the farmer in Iowa who gave Chipotle its first taste of free-range pigs a decade ago, to ask how the natural-pork business is changing.

To be sure, antibiotic-free meat still makes up a tiny share of the market. Economists estimate it's around 2 percent. But demand is growing.

"The marketplace for what we do has increased dramatically," he says. When he began working with Niman Ranch, which operates a bit like a co-op, he was the only pork farmer. Now there are hundreds.

"I'm proud that we've created a market for people who want to raise livestock this way," Willis told me.

And increasingly, consumers seem to be making the connections about what they eat. Concerns about antibiotic resistance in humans have led the Food and Drug Administration to issue voluntary guidelines that recommend limiting the use of antibiotics in livestock animals.

As consumer awareness has grown, Chef Greg Lopez of Hyatt Hotels says people are showing that they're willing to pay more for food that they perceive to be more healthful.

"I think we're at that groundswell moment, at that tipping point right now," he says.

Lopez says this month Hyatt announced it will offer antibiotic-free, naturally raised meat, poulty and dairy options at all of its hotels. The chain decided to expand these options, in part, after it saw the success of a natural burger on the menu. Meyer Natural Angus supplies those burgers.

"When they [consumers] were given a choice between just burger, and burger that was naturally raised and hormone-free, 30 percent paid a premium, a couple of bucks" to get the antibiotic-free option, Lopez says.

The list of retailers making changes is expanding. Wal-Mart sells a number of antibiotic-free beef and poultry products.

And as demand grows some farmers and suppliers are scrambling to adjust.

One sign of growing pains — temporary hiccups in the supply chain. Hyatt's Lopez says just this week his favorite all-natural chicken supplier — Palouse Pastured Poultry — told him it is temporarily sold out. "I'm in a dry spell," Lopez says. "Their next slaughter is scheduled for the last week of June or the first week of July."

Lopez says the good news is that there are more farmers ramping up this kind of production, so he'll be able to buy antibiotic-free chickens from another farm this month.

As for Behr, and the contribution of his "Lost Taste of Pork" article that helped chart a new course for Chipotle, I called him up to ask him about it.

"This is the one huge piece of good I've done through writing about food," he said with a laugh. "The one, huge, thing!"

Copyright 2013 NPR. To see more, visit http://www.npr.org/.

Transcript

MELISSA BLOCK, HOST:

This is ALL THINGS CONSIDERED from NPR News. I'm Melissa Block.

ROBERT SIEGEL, HOST:

And I'm Robert Siegel.

It's no longer a phenomenon exclusive to foodies and farmers markets. These days, more and more shoppers are buying naturally raised, antibiotic-free meat. Though it's still a small fraction of overall meat production in the U.S., it is expanding quickly. And in some cases, demand is outstripping supply.

NPR's Allison Aubrey looked into who's buying this meat and she found some surprising answers.

ALLISON AUBREY, BYLINE: If you've ever eaten in a Chipotle Mexican Grill, you may have experienced the crush of people at lunchtime. I approached a few customers who were waiting to order at this crazy-busy Chipotle in downtown D.C.

NATHAN ACKERMAN: I mean the line, visually, is daunting. Like, you look at it and you're like, I can't believe I'm going to walk into this place.

AUBREY: Nathan Ackerman and his colleague, Kevin Anthony, say it looks like it'll take forever, but they're usually in and out in 10 minutes or so.

KEVIN ANTHONY: It's pretty quick and you can pretty much custom-make your burrito, and it tastes good.

AUBREY: Nathan says he spends about eight bucks. And his favorite thing on the menu, tacos with pork, called carnitas.

ACKERMAN: Once I tried the pork, I was like game on - this is what I'm getting. It's not like anything been able to create at my house. It's delicious.

AUBREY: It is one of the most popular things on the menu. And how it got to be this way is the story of how this fast food company unexpectedly wandered off the beaten path. A decade ago, when Chipotle was just beginning to grow into the 1250-store chain it is today, it was having a hard time selling its pork carnitas.

I asked the company's Chris Arnold if they figured out why.

CHRIS ARNOLD: Yeah, in part because they weren't as good as other things on the menu.

AUBREY: Turns out taste and texture were an issue. In trying to figure it out, the founder of Chipotle, Steve Ells, stumbled upon an article called "The Lost Taste of Pork," published in a boutique-y food lover's journal called the Art of Eating. The article gave a detailed account of the page being raised on a family farm in Iowa, the old-fashioned way. Instead of pigs kept confined indoors and fed routine doses of antibiotics, as has become the norm, these pigs were outside grazing on pasture.

At the time the article was written in 1999, there was not a huge demand for antibiotic-free pork. They were sold through Niman Ranch who supplied specialty retailers and high-end restaurants. But then Chipotle decided to try some.

ARNOLD: We ordered pork from Niman and cooked with it and absolutely loved it. The eating qualities of pork from pigs raised this way is much, much better. The pigs develop more back fat to protect them from the elements, so you get a moister, more marbled meat.

AUBREY: That Arnold says his customers seemed to like better. Now, it's hard to know if they really detected a big difference, or if the in-store marketing about the switch to all natural, antibiotic-free pigs caught people's attention. But Arnold says what's clear is that the change worked, despite a considerable price jump.

ARNOLD: Our carnitas went from being 4.50 to 5.50, from the least expensive thing on the menu to the most expensive thing on the menu. And, of course, traditional fast-food wisdom would tell you that no one will buy it when you do that. What we saw is that we started selling twice as many carnitas as we had been before.

AUBREY: Now, every time they open a new location - which they plan to do in about 150 places this year - the demand for antibiotic-free meat expands. And not just for pork but also for chicken and beef. The company is now aiming to buy all of its meat, some 120 million pounds a year, from suppliers who meet its antibiotic-free standards.

And this is helping to create a lot of opportunity for farmers. I reached out to Paul Willis, the farmer in Iowa who gave Chipotle its first taste of free range pigs a decade ago, to ask how the natural pork business is changing.

PAUL WILLIS: The marketplace for what we do has increased dramatically.

AUBREY: I caught him on his cell phone about 8 A.M., as he was checking on his pigs. The sound of goldfinches was faint in the background of our muffled connection.

WILLIS: It's a beautiful morning, you know. The sun has been up a while and there's dew on the grass. And the sows, they're out grazing.

AUBREY: Willis says there was a time when his livelihood was threatened. He was struggling to compete with all of the big pork producers. But he says he didn't want to adopt their model of raising pigs in cramped buildings. He didn't think it was right. Farmers like him were leaving the business. But now, with a national distribution chain and a growing list of big customers, such as Chipotle and, of course, Whole Foods, it's a model that's working.

WILLIS: I'm proud of the fact that we created a market for people who want to raise livestock in this way. Without these markets a lot of these farmers wouldn't be raising pigs at all.

AUBREY: What began with Willis and a few other farmers have grown to include hundreds of farmers and ranchers, including lamb and beef producers, marketing their products through Niman Ranch, which operates a bit like a co-op.

WILLIS: We are soon to reach the number of farmers and ranchers at 700.

AUBREY: Wow, that's incredible growth. Isn't it?

WILLIS: Well, yes. I mean I...

(LAUGHTER)

WILLIS: ...who would have thought when we started?

AUBREY: Lots of people today are curious about where their meat comes from and how the animals are treated. And because of concerns about antibiotic resistance in humans, the Food and Drug Administration has issued voluntary guidelines that recommend limiting the use of antibiotics in livestock animals.

Science aside, Chef Greg Lopez, of Hyatt Hotels, says to him what seems clear is that consumer sentiment is shifting. Hyatt announced earlier this month that all of its hotels will begin offering antibiotic-free meat and poultry options.

GREG LOPEZ: I think we are at that groundswell moment that we're kind of at that tipping point right now - you know, today, this month, this year.

AUBREY: He says lots of people are willing to pay a little more for food they perceive to be healthier. Hyatt found this with its customers during a trial run with hamburgers.

LOPEZ: When they were given the choice between just a burger and a burger that was naturally raised and hormone-free, 30 percent of them paid a premium, a couple bucks, to get the natural product.

AUBREY: It's not just fancy hotel chains offering these meats. The nation's largest retailer, Wal-Mart, sells a number of antibiotic-free beef and poultry products. And there's institutional food providers, such as Bon Appetite, catering to colleges and companies. In some cases, demand is growing so fast, farmers and suppliers are scrambling to adjust.

Hyatt's Greg Lopez says one consequence is that there can be temporary pickups. Just this week, his favorite all natural chicken supplier, an operation called Palouse Pastured Poultry, told him they're temporarily sold out.

LOPEZ: I'm in a dry spell right now for the month of June. Their next slaughter is - I believe it's scheduled the last week of June, first week of July.

AUBREY: Lopez says the good news is that there are many more farmers ramping up this kind of production. So, for this month, he'll be able to buy antibiotic-free chickens from another farm. Allison Aubrey, NPR News. Transcript provided by NPR, Copyright NPR.